1 Technical Field
This disclosure relates generally to a sensor designed to have a junction between an electrode terminal of a sensor device and a contact spring.
2 Background Art
Japanese Patent First Publication No. 2010-223615 teaches a gas sensor for use in measuring the concentration of a given gas component such as oxygen or NOx (nitrogen oxide) contained in exhaust emissions flowing through an exhaust pipe of an internal combustion engine. The gas sensor has a plurality of electrode terminals which are disposed on a sensor device and are connected to a plurality of electrical terminals in the form of contact springs joined to a plurality of lead wires, respectively. Each of the electrical terminals is made up of a terminal connecting portion which has a spring contacting one of the electrode terminals and a crimp portion which is joined to one of the lead wires.
The electrical terminals are retained inside a terminal cover member. The lead wires pass through holes formed in an elastic sealing member, respectively. The terminal cover member and the elastic sealing member are arranged inside a metallic protective cylinder. The elastic sealing member and the lead wires are retained by the protective cylinder which has a peripheral wall partially crimped to have a decreased diameter.
The crimping of the protective cylinder usually results in elastic deformation of the elastic sealing member, which leads to deformation of the lead wires. This causes external force to be exerted radially outwardly on a boundary between the terminal connecting portion and the crimp portion of each of the electrical terminals joined to the lead wires to bend the crimp portion. Tension stress arising from the bending of the crimp portion remains in the boundary.
When or after the gas sensor is installed in the exhaust pipe, the lead wires are usually pulled outside the gas sensor, so that such pulling acts on the boundaries in the form of tension stress. Two kinds of tension stresses are, therefore, simultaneously applied to the boundaries.
The simultaneous application of the tension stresses to the boundaries results in need for increasing the mechanical strength of the electrical terminals, thus resulting in difficulty in reducing the size or thickness of the electrical terminals. If, therefore, it is necessary to increase the electrical terminals and the lead wires, but the overall size of the gas sensor needs to be decreased, reduction in size or thickness of the electrical terminals requires changing how the stresses act on the electrical terminals.